MONDAY, March 24, 2014 (HealthDay News) -- Contrary to some advertising claims, electronic cigarettes don't help people quit or cut down on smoking, a new study says.

Users of e-cigarettes inhale vaporized nicotine but not tobacco smoke. The unregulated devices have been marketed as smoking-cessation tools, but studies to date have been inconclusive on that score, the study noted.

"When used by a broad sample of smokers under 'real world' conditions, e-cigarette use did not significantly increase the chances of successfully quitting cigarette smoking," said lead researcher Dr. Pamela Ling, an associate professor at the Center for Tobacco Control Research and Education at University of California, San Francisco.

These findings -- based on nearly 1,000 smokers -- are consistent with other studies and contradict the claims frequently found in e-cigarette advertising, she said.

"Advertising suggesting that e-cigarettes are effective for smoking cessation should be prohibited until such claims are supported by scientific evidence," Ling said.

For the study, Ling's team analyzed data reported by 949 smokers, 88 of whom used e-cigarettes at the start of the study.

One year later, 14 percent of the smokers had quit overall, with similar rates in both groups.

"We found that there was no difference in the rate of quitting between smokers who used an e-cigarette and those who did not," Ling said.

There was no relationship between e-cigarette use and quitting, even after taking into account the number of cigarettes smoked per day, how early in the day a smoker had a first cigarette and intention to quit smoking, Ling added.

However, the researchers noted that the small number of e-cigarette users may have limited the ability to find an association between e-cigarette use and quitting.

The report, published online March 24 in JAMA Internal Medicine, also found that women, younger adults and people with less education were most likely to use e-cigarettes.

One expert said the study is flawed and shouldn't be taken seriously.

"It's an example of bogus or junk science," said Dr. Michael Siegel, a professor of community health sciences at Boston University School of Public Health.

"That's because the study does not examine the rate of successful smoking cessation among e-cigarette users who want to quit smoking or cut down substantially on the amount that they smoke, and who are using e-cigarettes in an attempt to accomplish this," Siegel said. "Instead, the study examines the percentage of quitting among all smokers who have ever tried e-cigarettes for any reason."

Many of the smokers who tried e-cigarettes may have done so out of curiosity, Siegel said.

"It is plausible, in fact, probable, that many of these 88 smokers were not actually interested in quitting or trying to quit with electronic cigarettes," he said. "These products have become very popular and have gained widespread media attention, and it is entirely possible that many of these smokers simply wanted to see what the big fuss is all about."

Calling that a "fatal flaw" in the research, Siegel said it "destroys the validity of the authors' conclusion."

It would be a tragedy, he said, if policy makers use the study to draw conclusions about the effectiveness of e-cigarettes for smoking cessation purposes.

Erika Ford, assistant vice president for national advocacy at the American Lung Association, said the study confirms what is already clear -- "e-cigarettes are not associated with quitting among smokers."

Ford noted that most e-cigarette companies no longer make claims that their products help smokers quit. "But there is a need for the FDA [U.S. Food and Drug Administration] to begin their oversight of these products. It's time for the FDA to find out which products are making no smoking claims and which ones might be in violation of current law," she said.

The FDA plans to introduce regulations for e-cigarettes, but hasn't yet. In the past, the agency has warned companies about making false claims and for poor manufacturing practices.